Oncogenic Ras/Her-2 mediate hyperproliferation of polarized epithelial cells in 3D cultures and rapid tumor growth via the PI3K pathway
Oncogenic Ras/Her-2 mediate hyperproliferation of polarized epithelial cells in 3D cultures and rapid tumor growth via the PI3K pathway
复制标题
DOI：
10.1038/sj.onc.1205661
复制
发表时间：
2002-08-01
期刊：
影响因子：
8
通讯作者：
Beug, H
中科院分区：
文献类型：
--
作者：
Janda, E;Litos, G;Beug, H
致癌的RAS和HER-2致癌涉及促进体内上皮细胞的增殖。然而，这些癌基因或它们的下游途径在体外诱导的过度增殖主要是在培养的成纤维细胞系中进行的研究。在这里，我们证明了致癌的Ha-RAS或结构性活性的HER-2导致完全极化的乳腺上皮细胞(EpH4)的增殖增加和细胞周期蛋白D1上调，如果在三维胶原/基质中培养为器官型结构的话。然而，在标准培养条件下，这些癌基因不能诱导过度增殖。使用特定的低分子质量抑制剂和RAS效应特异性突变体，我们剖析了致癌RAS下游的信号通路(PI3K，MEK1/MAPK)，这些信号通路与(I)胶原凝胶中的过度增殖和小鼠肿瘤的发生以及(Ii)上皮/间充质转化(EMT)有关。我们发现，RAS激活的PI3K通路在胶原胶中诱导肿瘤快速生长和促进EPH4细胞的增殖是必需的，但在体外和体内都不能引起EMT。另一方面，依赖RAS的MEK1/MAPK通路在EpH4细胞中的激活(先前被证明会导致EMT和转移)不会在胶原凝胶中诱导过度增殖，只会导致缓慢的肿瘤生长。因此，我们的数据表明，RAS依赖的信号通过PI3K和MAPK通路在癌变过程中发挥不同但互补的功能。
Carcinogenesis by oncogenic Ras and Her-2 involves enhanced proliferation of epithelial cells in vivo. However, hyperproliferation induced by these oncogenes, or their downstream pathways in vitro has mainly been studied in cultured, fibroblastic cell lines. Here, we demonstrate that oncogenic Ha-Ras or constitutively active Her-2 cause increased proliferation and cyclin D1 upregulation in fully polarized, mammary epithelial cells (EpH4), if cultivated as organotypic structures in three-dimensional collagen/ matrigel matrices. Under standard culture conditions, however, these oncogenes failed to induce hyperproliferation. Using both specific low molecular weight inhibitors and Ras-effector - specific mutants, we dissected signaling pathways downstream of oncogenic Ras (PI3K, Mek1/ MAPK) with respect to (i) hyperproliferation in collagen gels and tumorigenesis in mice and (ii) epithelial/ mesenchymal transition (EMT). We show that the Ras-activated PI3K pathway is required to induce rapid tumor growth and enhanced proliferation of EpH4 cells in collagen gels, but fails to cause EMT in vitro and in vivo. On the other hand, Ras-dependent activation of the Mek1/ MAPK pathway in EpH4 cells (previously shown to cause EMT and metastasis) did not induce hyperproliferation in collagen gels and caused only slow tumor growth. Our data thus indicate that Ras-dependent signaling through the PI3K- and MAPK pathways fulfil distinct, but complementary functions during carcinogenesis.